1. Field of the Invention
The invention relates generally to display systems and, more specifically, to a method and apparatus to support a self-refreshing display device coupled to a graphics controller.
2. Description of the Related Art
Some recently designed display devices include a self-refresh capability, where the display device includes a local controller configured to generate video signals from a static, cached frame of digital video independently from the graphics controller. When in such a self-refresh mode, the video signals are driven by the local controller, thereby allowing portions of a parallel processing system, such as the graphics controller and a communications bus, to be placed in a deep sleep state to conserve power. Once in self-refresh mode, when the image to be displayed needs to be updated, control may be transitioned back to the graphics controller to allow new video signals to be generated based on a new set of pixel data.
Conventional systems are configured to initialize the various interconnected components in a serial manner. For example, the central processing unit may first cause a driver to make a call to wake-up the communications bus. An initialization routine is run to configure the communications bus. Once the communications bus is operating in a normal state, the central processing unit may then cause a driver to make a call to wake-up the graphics controller. The graphics driver then sends commands via the communications bus to the graphics controller to initialize the graphics controller.
One drawback to the above described technique is that each component of the parallel processing subsystem must be initialized in order before the next component can begin its initialization process. For example, while the communications bus is initialized, the graphics controller may sit idle waiting to receive commands over the communications bus. The described technique fails to minimize the number of clock cycles in which the graphics driver is initialized upon waking from a deep sleep state. Extended initialization routines may lead to latency in graphics updates and could be distracting to a user of the computer system when entering and exiting a panel self-refresh mode.
As the foregoing illustrates, what is needed in the art is an improved technique for waking-up the graphics controller from a deep sleep state.